Interpretive Summary: The varroa resistance of several genetic crosses utilizing ARS Russian honey bees was tested in Alabama during 2001. Bee stocks included pure ARS Russian (Russian queens × Russian drones), commercial (commercial queens × commercial drones), Russian hybrids (commercial queens × Russian drones), and SMR-Russian hybrids [(queens bred for the suppression of mite reproduction trait) × Russian drones]. The varroa resistance of Russian hybrids was intermediate to that of pure ARS Russian and commercial stocks. This suggests that Russian hybrids may offer some varroa resistance, but pure ARS Russian stock should be used to achieve the maximum varroa resistance that is currently available in Russian bees. The lowest growth of mite populations occurred in the SMR-Russian hybrids. This may suggest that resistance genes from the ARS Russian bees and SMR bees combine to produce more varroa resistance than occurs in the average Russian-commercial hybrid. We cannot be sure because pure SMR bees (SMR queens × SMR drones) were not included in the study.

Technical Abstract:
Pure ARS Russian honey bees are significantly resistant to both varroa and tracheal mites. One frequently asked question about them is 'What level of resistance can be expected from hybrid Russian bees?' This consideration is important given the increased marketing of various hybrid Russian bees as 'Russian honey bees.' We tested the varroa resistance of several genetic crosses utilizing ARS Russian honey bees in Alabama during 2001. The tested stocks included pure ARS Russian (Russian queens × Russian drones), commercial (commercial queens × commercial drones), Russian hybrids (commercial queens × Russian drones), and SMR-Russian hybrids [(queens bred for the suppression of mite reproduction trait) × Russian drones]. Colonies were inoculated with 93 ±27 mites per colony in early June, and mite populations were allowed to grow for 17 weeks.
Although the final mite populations were not significantly different among the 4 types of bees, Russian hybrids had mite populations intermediate to those of commercial stocks (highest) and pure ARS Russian stocks (low). SMR-Russian hybrids had the lowest mite populations. Pure ARS Russian stock had a significantly lower percentage of mites in capped brood (48 %) than either commercial stocks or Russian-SMR hybrids (both had 58-60 %). Russian hybrids had an intermediate value (ca. 53 %). This result is important for two reasons: (1) most of the harm caused to a colony of bees by varroa mites results from infestation of capped worker brood, and (2) a lower percentage of mites in capped brood may suggest that mites spend more time on adult bees between the reproductive bouts which occur within capped cells. This latter effect would slow growth of varroa mite populations. Thus, it appears that Russian hybrids are less varroa resistant than pure ARS Russian bees but more resistant than commercial stocks. Beekeepers wanting resistance to varroa mites should insist upon pure ARS Russian honey bees produced by reputable queen breeders with a well-established Russian honey bee breeding program or those that use instrumental insemination to produce pure Russian queens. The lowest growth of mite populations occurred in the SMR-Russian hybrids. This may suggest that resistance genes from the two parental types combine in an additive manner, but we cannot be sure because pure SMR bees (SMR queens × SMR drones) were not included in the study.